1. Field of the Invention
The present invention generally relates to implants and methods to reshape tissue and, more specifically, to dynamically reshape and resize the mitral valve annulus of a heart.
2. Description of the Related Art
In recent years, hundreds of thousands of individuals have undergone mitral valve replacement or repair. The mitral valve is a portion of the heart that is located between the chambers of the left atrium and the left ventricle. When the left ventricle contracts to pump blood throughout the body, the mitral valve closes to prevent the blood from being pumped back into the left atrium. In some individuals, whether due to genetic malformation, disease or injury, the mitral valve fails to close properly, causing a condition known as mitral regurgitation, whereby blood is pumped into the atrium upon each contraction of the heart muscle.
Mitral regurgitation is a serious, often rapidly deteriorating, condition that reduces circulatory efficiency. Oftentimes, mitral regurgitation is caused by geometric changes of the left ventricle, papillary muscles and mitral annulus. For example, certain diseases of the heart valves can result in dilation of the heart and one or more heart valves. When a heart valve annulus dilates, the valve leaflet geometry deforms and causes ineffective closure of the valve leaflets. The ineffective closure of the valve, or incomplete coaptation of the valve leaflets, can cause regurgitation of the blood, accumulation of blood in the heart and other problems.
Two of the more common techniques for restoring the function of a damaged mitral valve are valve replacement surgery and annuloplasty. In valve replacement surgery, the damaged leaflets are surgically excised, and the mitral valve annulus is sculpted to receive a replacement mechanical valve. In annuloplasty, the effective size of the valve annulus is contracted by attaching a prosthetic annuloplasty repair segment or ring to an interior wall of the heart around the valve annulus. The annuloplasty ring reinforces the functional changes that occur during the cardiac cycle to improve coaptation and valve integrity. Thus, annuloplasty rings help reduce reverse flow or regurgitation while permitting good hemodynamics during forward flow.
Each of these procedures, however, is highly invasive because access to the heart is obtained through an opening in the patient's chest, with the heart being bypassed to a heart-lung machine throughout the procedure. Most patients with mitral valve regurgitation, however, are often relatively frail, thereby increasing the risks associated with such an operation.
In response to the foregoing drawbacks, less invasive approaches have been proposed for aiding the closure of the mitral valve. These procedures involve the percutaneous placement of a manually-adjustable support structure in the coronary sinus close to the posterior leaflet of the mitral valve. The support structure is designed to push the vessel and surrounding tissue toward the anterior wall of the valve to aid its closure and to improve leaflet coaptation. This procedure, however, has several drawbacks. For example, the support structure does not allow for non-invasive alteration or adjustment and is oftentimes permanently implanted within the patient. Furthermore, a surgeon is unable to reduce the force of the support structure to reduce risk of artery pinching and is further unable to readjust the shape and size of the support structure post-implant or during the implantation.